A 45-year-old presents with progressive 5-day ascending weakness, areflexia, FVC 1.1 L (predicted 4.0) and a weak cough. How do you manage?

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This patient has **rapidly progressive neuromuscular respiratory failure** — FVC 1.1 L is critical. My priority is **respiratory protection first, diagnosis in parallel**.

**ABCDE.** Sit up, monitor closely. Do **not** be reassured by a normal SpO2 — in neuromuscular weakness, **SpO2 and ABG fall late, after the airway is unsafe**. The decisive bedside tools are **FVC, maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), single-breath count, and bulbar function**.

The **20/30/40 rule** mandates ITU and consideration of intubation when:
- **FVC <20 ml/kg** (or <1 L absolute, or 30% predicted) — this patient is there
- **MIP <30 cmH2O**
- **MEP <40 cmH2O**

Phone **ITU and anaesthetics now**; pre-emptive **elective intubation** is safer than crash intubation in a tiring patient with bulbar weakness.

**Diagnosis — parallel workup.**
- **Guillain-Barré:** areflexia, ascending weakness, recent gastroenteritis or URTI, autonomic dysfunction. **LP at 1 week** shows **cytoalbuminologic dissociation** (high protein, normal cell count). **Nerve conduction studies** support demyelinating or axonal subtype.
- **Myasthenic crisis:** fatigability, ptosis, diplopia, bulbar symptoms, **AChR or MuSK antibodies**, ice-pack test, response to edrophonium (rarely used). Often triggered by infection, surgery, or drugs (aminoglycosides, beta-blockers, magnesium).

**Treatment.**
- **GBS:** **IVIG 0.4 g/kg/day for 5 days** or **plasma exchange** — equivalent efficacy. **Steroids are NOT indicated** in GBS. Supportive care — VTE prophylaxis, neuropathic pain control (gabapentin), nutritional support, MDT rehab from day 1.
- **Myasthenic crisis:** **plasma exchange** (faster in crisis) or IVIG, **adjust pyridostigmine** (excess can cause cholinergic crisis), **high-dose steroids** with caution (initial worsening), **avoid precipitants** (magnesium, aminoglycosides, beta-blockers, fluoroquinolones).

**Monitor for autonomic GBS** — labile BP, arrhythmias, ileus, urinary retention — ECG monitoring on ITU.

**Communication.** Honest conversation with family about prolonged ITU course, tracheostomy planning, and recovery prognosis. **MDT** — neurology, ITU, physiotherapy, OT, SALT, dietitian, psychology. **Refer to tertiary neurology** for specialist input.

Document the FVC trend carefully — it is the single most important predictor.

Rapid-onset neuromuscular weakness with respiratory compromise — GBS vs myasthenic crisis

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